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-Ai Si 599 MAXIMUM THEORETICAL SPECIFIC GRAVITY OF BITUMINOUS 1/1PAVING MIXTURESU) ARMY ENGINEER WATERWAYS EXPERIMENTSTATION VICKSBURG HS GEOTE R R JOHNSON ET A APR 87
UNCLASSIFIED WES/TR/GL'-87-8 F/G ii/7 N
'lll.
LiIMBS&
ma MA
IL.
11-I5
/.. TECHNICAL REPORT GL-87-8
MAXIMUM THEORETICAL SPECIFIC GRAVITYoOF BITUMINOUS PAVING MIXTURES
by MC FILE COPYRobert R. Johnson, Karen L. Kelley
AD-A 181 599 Geotechnical Laboratory
DEPARTMENT OF THE ARMYWaterways Experiment Station, Corps of Engineers
PO Box 631, Vicksburg, Mississippi 39180-0631
April 1987
Final Report
Approved For Public Release; Distribution Unlimited
DTICSELECTEJUN 2 5 1987D
%~ EN~ Prepared for DEPARTMENT OF THE ARMY
LABORATORY' US Army Corps of EngineersWashington, DC 20314-1000
67 6 25 008
Destroy this report when no longer needed. Do not returnit to the originator.
The findings in this report are not to be construed as an officialDepartment of the Army position unless so designated
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The contents of this report are not to be used foradvertising, publication, or promotional purposes.Citation of trade names does not constitute anofficial endorsement or approval of the use of
such commercial products.
SECURITY CLASSIFICATION OF THIS PAGE
Form ApprovedREPORT DOCUMENTATION PAGE OMB No 0704.O188Exp Date Jun 30, 1986
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Technical Report GL-87-8
6a. NAME OF PERFORMING ORGANIZATION 6b. OFFICE SYMBOL 7a. NAME OF MONITORING ORGANIZATIONUSAEWES (If applicable)Geotechnical Laboratory
6c. ADDRESS (Cy, State, and ZIP Code) 7b. ADDRESS (City, State, and ZIP Code)
PO Box 631Vicksburg, MS 39180-0631
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Washington, DC 20314-1000
1 . TITLE (Include Security Classification)
Maximum Theoretical Specific Gravity of Bituminous Paving Mixtures
12. PERSONAL AUTHOR(S)Johnson, Robert R., Kelley, Karen L.13a. TYPE OF REPORT 13b. TIME COVERED 14. DATE OF REPORT (Year, Month, Day) 15. PAGE COUNTFinal report FROM TO April 1987 30
16. SUPPLEMENTARY NOTATIONAvailable from National Technical Information Service, 5285 Port Royal Road,Springfield, VA 22161
17. COSATI CODES 18. SUBJECT TERMS (Continue on reverse if necessary and identify by block number)FIELD GROUP SUB-GROUP Apparent specific gravity
' BulIlmpregnated specific gravity
19. ABSTRACT (Continue on reverse if necessary and identify by block number)
To calculate the percentage of voids in a bitumao.1s pavement mixture, it is neces-sary to determine the maximum theoretical specific gravity'of the mixture. Test proce-dures being used to determine the maximum theoretical specific 'avity of bituminousmixtures made with absorptive aggregates have proved to be troublesome. The specifiedprocedure has also been found to be questionable when used for recy'eled asphalt pavementtesting. This report discusses and compares test results and void calculations when dif-fe rent test procedures are used to determine the maximum theoretical specific gravity ofabsorptive aggregates in bituminous mixtures. (k - -
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PREFACE
This study was conducted by the Geotechnical Laboratory (GL), US Army
Engineer Waterways Experiment Station (WES), Vicksburg, Mississippi, for the
Office, Chief of Engineers (OCE), US Army, under the Facilities Investigation
and Studies Program. Mr. A. F. Muller, OCE, was the Technical Monitor. This
report describes the results obtained from the project entitled "Theoretical
Maximum Specific Gravity of Bituminous Paving Mixtures."
The study was conducted under the general supervision of Dr. W. F.
Marcuson III, Chief, GL; Mr. H. H. Ulery, Jr., Chief, Pavements System Divi-
sion (PSD), GL; Mr. J. W. Hall, Jr., Chief, Engineering Investigation, Test-
ing, and Validation Group (EIT&V), PSD, GL; and Dr. E. R. Brown, Chief,
Material Research Center, EIT&V, PSD, GL. Personnel of PSD actively engaged
in the planning, testing, analyzing, and reporting phases of this study were
Mr. R. R. Johnson, Ms. K. L. Kelley, Mr. L. N. Lynch, Mr. R. T. Graham, and
Mr. J. K. Simmons. This report was written by Mr. Johnson and Ms. Kelley,
PSD.
COL Allen F. Grum, USA, was the previous Director of WES. COL Dwayne G.
Lee, CE, is the present Commander and Director. Dr. Robert W. Whalin is Tech-
nical Director.
Aooession Tor
DTIC TABUnannounced [3JustifiCation
Distributlon/
Availability Codes KAvail and/or
Dist Special
i1
CONTENTS
Page
PREFACE . .. .. .. .. .. . .. . .. .. .. .. .. .. . .. . 1
CONVERSION FACTORS, NON-SI TO SI (METRIC) UNITS OFMEASUREMENT . . .. .. .. .. .. .. .. .. .. .. .. .. .... 3
PART I: INTRODUCTION .. .. .. .. .. .. .. .. .. .. ..... 4
Background ......... .. .. .. .. .. .. .. .. .. ... 4Objective. ... .................. ........ 5Scope .. ........... .................... 5
PART II: TESTING PROGRAM........... . ... .. .. .. .. ... 7
B last Furnace Slag . . .. .. .. .. .. .. .. .. .. .... 7Florida Limerock ... .......... .. .. .. .. .... 12Alabama Limestone .. ........... ............. 15Crushed Gravel . .. .. . .. . . .. .. .. .. .. .. .... 15
PART III: DISCUSSION .. ........... .............. 23
PART IV: CONCLUSIONS. ........... .............. 26
REFERENCES . .. .. .. .. .. .. .. .. .. .. .. .. .. .... 27
2
V. 9 'V
CONVERSION FACTORS, NON-SI TO SI (METRIC)UNITS OF MEASUREMENT
Non-SI units of measurement used in this report can be converted to SI
(metric) units as follows:
Multiply By To Obtain
cubic feet 0.02831685 cubic metres
inches 2.54 centimetres
pounds (force) per square inch 6.894757 kilopascals
pounds (mass) 0.4535924 kilograms
3
MAXIMUM THEORETICAL SPECIFIC GRAVITY OF
BITUMINOUS PAVING MIXTURES
PART I: INTRODUCTION
Background
1. The maximum theoretical specific gravity of bituminous paving mix-
tures is the specific gravity at which zero air voids are present in the mix.
There are currently three methods commonly being used by asphalt technologists
to determine the maximum theoretical specific gravity: (a) a computation
using the apparent specific gravity of the aggregate and asphalt cement; (b) a
computation based on the bulk-impregnated specific gravity; and (c) a measure-
ment in accordance with American Society for Testing and Materials' (ASTM)
D 2041. Presently, the Corps of Engineers allows only methods (a) and (b) to
be used (Headquarters, Department of the Army 1971).
2. Corps of Engineers specifications for asphalt concrete require that
Test Method 105 (Military Standard 620A) entitled "Determination of Bulk-
Impregnated Specific Gravity of Aggregate Proposed for Use in Bituminous Pav-
ing Mixes," be used for determining the specific gravity of aggregate blends
having a water absorption in excess of 2.5 percent (Department of Defense
1966). Problems have been experienced with this test procedure primarily
because of the unfamiliarity of laboratory technicians with the test.
3. Test Method 105 specifies that 85 to 100 penetration grade asphalt
be used in the test. If another grade of asphalt cement is used in the field,
this makes the tests with 85 to 100 penetration grade asphalt cement somewhat
erroneous. Requiring the job asphalt cement to be used in determining the
bulk-impregnated specific gravity would be more realistic and should be speci-
fied if use of this procedure is continued.
4. Past experience has also indicated that the bulk-impregnated spe-
cific gravity test procedure has produced wide variations in results on iden-
tical samples when the tests are conducted by different operators. Most
laboratories have not had experience with this test method because the Corps
of Engineers is the only agency using it. There is an obvious advantage in
4
selecting a method in common use for determining maximum theoretical specific
gravity.
5. Additional problems have been encountered when determining specific
gravities for the materials used in recycled asphalt pavements. The technique
using apparent specific gravity requires the specific gravities of virgin
materials and the reclaimed asphalt pavement materials to be combined to cal-
culate the properties of the recycled mixture. To obtain the specific gravi-
ties of the reclaimed asphalt, extractions of large samples of the material
are necessary. Following extraction, the aggregates are separated into fine
and coarse aggregates, and the specific gravity is determined for each size
range. Also, after the extraction test, the asphalt is separated from the
solvent and the asphalt specific gravity is determined. Some recycled materi-
als require the addition of a recycling agent (RA), and the specific gravity
of this material is also required. Percentages of the separate components are
used in calculating the maximum theoretical specific gravity of the mixture.
With this large number of materials, these procedures are cumbersome and
require that tests be conducted by an experienced technician to minimize the
margin of error.
Objective
6. The objective of this study was to determine, through a literature
review and a testing program, the feasibility of replacing the bulk-
impregnated specific gravity procedure with the test method described in
ASTM D 2041 for determining maximum theoretical specific gravity of mixes con-
taining absorptive aggregates. A comparison was also made between the maxi-
mum theoretical specific gravity, measured in accordance with ASTM D 2041, and
the maximum theoretical specific gravity computed from the apparent specific
gravity.
Scope
7. The objectives of this study were accomplished by a review of
(a) the ASTM procedures, (b) American Association of State Highways and Trans-
portation Officials (AASHTO) testing procedures, and (c) the ITS Army Engineer
Waterways Experiment Station reports written during the development of the
5
bulk-impregnated specific gravity test procedure (US Army Engineer Waterways
Experiment Station 1953; Buck 1954; Department of Defense 1966; McRae 1955,
1956a, 1956b). In addition to the literature review, a testing program was
conducted using two absorptive aggregates and two nonabsorptive aggregates.
The maximum theoretical specific gravity was calculated from the measured
bulk-impregnated specific gravity for asphalt mixture prepared with the two
absorptive aggregates and compared with the maximum theoretical specific grav-
ity determined from ASTM D 2041. This information was used to calculate the
voids of the two mixtures at various asphalt contents to evaluate differences
in the two test methods. The maximum theoretical specific gravity was com-
puted from the apparent specific gravity for asphalt mixture prepared with the
two nonabsorptive aggregates and compared with the maximum theoretical spe-
cific gravity determined from ASTM D 2041. This information was used to
calculate and compare the voids of the two mixtures at various asphalt
contents.
6
PART II: TESTING PROGRAM
8. Four aggregates were selected for the study: (a) blast furnace
slag; (b) Florida limerock from Maule Industries, Miami, Florida; (c) Alabama
limestone from Vulcan Materials Company, Birmingham, Alabama; and (d) crushed
gravel from Runyon and Sons, Vicksburg, Mississippi. Both the blended grada-
tion of the slag and the blended gradation of the Florida limerock had a water
absorption in excess of 2.5 percent. The blended gradation of the Alabama
limestone and the blended gradation of the crushed gravel had a water absorp-
tion less than 2.5 percent. The apparent specific gravity and absorption for
each of these aggregates are provided in Table 1.
Table 1
Aggregate Test Results
Apparent Percent Absorption
Aggregate Specific Gravity of Blend
Slag 2.694 3.90
Florida limerock 2.638 3.89
Alabama limestone 2.735 0.49
Crushed gravel 2.641 1.15
Blast Furnace Slag
9. A mix design was prepared for the slag aggregate and AC 20 asphalt
cement. Samples at a number of asphalt contents were mixed and the samples
were split, with one-half of each sample used to prepare Marshall specimens
and the other half used to determine the maximum theoretical specific gravity
in accordance with ASTM D 2041. The gyratory compactor, set at 100 psi,*
1-deg angle, and 30 revolutions (similar to 50-blow compaction with Marshall
hammer), was used to compact the specimens in accordance with Military Stan-
dard 620A (Method 102).
* A table of factors for convertitig non-SI units of measurement to SI
(metric) units is presented on page 3.
7
10. Results of mix design tests conducted on the compacted samples are
shown in Figures I and 2. A comparison of the voids filled and voids total
mix computed from the bulk-impregnated specific gravity and the ASTM D 2041
maximum theoretical specific gravity is shown in Figure 3. The values for the
two methods are approximately equal. The maximum theoretical specific gravi-
ties used for the void calculations at the various asphalt contents are listed
in Table 2. The results are similar for the two methods. The test results
135 8
S7
_-Q 134 6< 0
00
t 133 4 4
nw w
cr 3WCL
132 1 1 1 2 1 1 1 I
2000 95 -
1900 - 90
,1800 . 85,,
501700
C- C 80
co SLA
LI-
I- 160w 75
1500 ~-70
1400I I I 65
25 8.5 9.0 9.5 10.0 10.5
BITUMEN CONTENT, %wU 20
X SLAG15 AC 20
GYRATORY COMPACTOR10 ~ 100 PSIi 0, 30 REVOLUTIONS
0-3 5LL
08.5 9.0 9.5 10.0 10.5
BITUMEN CONTENT,.
Figure 1. Slag aggregate mix design. Voids calculatedusing bulk-impregnated specific gravity
]8
. kip "'.I
L ai 1926& -
135 8fx7
134 0 -
00
5
t"- 133 - 4z z
C.w
132 2 I I
2000 95
1900 - 90
4. 1800 - 85
t-1700 -80 ca 4z
1600 w 75
0 LU
1500 C. 70
1400 I I I 65 I I25 8.5 9.0 9.5 10.0 10.5
BITUMEN CONTENT, %LU20
0 SLAG-- 1 AC 20
15 0C2oGYRATORY COMPACTOR
10 100 PS,1, 30 REVOLUTIONS
NOTE: PLOTS FOR UNIT WEIGHT,O STABILITY, AND FLOW ARE THE
1 5-. SAME AS THOSE IN FIGURE 1.
0II I8.5 9.0 9.5 10.0 10.5
BITUMEN CONTENT, %
Figure 2. Slag aggregate mix design. Voids
calculated using theoretical maximum specific
gravity--ASTM D 2041
9
SLAG100
90w -------------------
SPECIFICATION LIMITS'a. 50-BLOW DESIGN a_j + 2.5% ABSORPTION
U. 8
0
SMAXIMUM THEORETICAL70 SPECIFIC GRAVITY
ASTM D 2041
- BULK-IMPREGNATEDSPECIFIC GRAVITY
60
8--4MAXIMUM THEORETICAL
SPECIFIC GRAVITY
h--- BULK-IMPREGNATED
I-T
O SPECIFICATIONRLIMIT
> 50-BLOW DESIGN+ 2.5% ABSORPTION
8.5 9.0 9.5 10.0 10.5BITUMEN CONTENT, %
Figure 3. Slag aggregate mix design.Comparison of voids filled and voids
total mix
10
Table 2
Comparison of Maximum Theoretical Specific Gravities
Slag Aggregate
Percent Asphalt ASTM D 2041 Method Bulk-Impregnated Method
8.5 2.284 2.289
9.0 2.280 2.274
9.5 2.242 2.259
10.0 2.245 2.244
10.5 2.212 2.229
determined by ASTM D 2041 were an average of two tests conducted on the mate-
rial taken from the split sample, whereas the bulk-impregnated specific gravi-
ties were calculated from an average of four tests.
11. The two test procedures were also investigated to compare the vari-
ability of the test methods. Six individual tests were conducted on identical
materials using the two test methods so that the standard deviation could be
calculated (Table 3). The results indicate that there is very little differ-
ence in variability between the two methods; however, personnel familiar with
both test methods conducted these laboratory tests.
Table 3
Comparison of Reproducibility Slag Aggregate
Slag Aggregate
Test Number ASTM D 2041 Method Bulk-Impregnated Method
1 2.258 2.281
2 2.259 2.304
3 2.252 2.304
4 2.286 2.302
5 2.261 2.318
6 2.241 2.309
Average 2.260 2.303
Standard Deviation 0.015 0.012
11
Florida Limerock
12. The same tests conducted on the slag aggregates were also conducted
on the Florida limerock aggregate. During mixing, it was noticed that the
mixture contained porous uncoated aggregate; therefore, the supplemental pro-
cedure in ASTM D 2041 was used to determine the maximum theoretical specific
gravity. The supplemental procedure involves using the saturated surface dry
weight of the sample to calculate the specific gravity. This procedure is
noted and specified in ASTM D 2041 as well as AASHTO T 209 as a "Supplemental
Procedure for Mixtures Containing Porous Aggregate Not Completely Coated."
13. Results of mix design tests conducted on the compacted samples are
shown in Figures 4 and 5. A comparison of the voids filled and the voids
133 - 12 -x
132 - z 10 -i
- 131 - 8 -Z0
2 130 - 6
>It 129 4 4
z z
S128 2r 2
127 fI 0 / I
2000 95 -
1900 90 O
~1800 as85
U
I-1600 75Ur
1500 CL70
1400 65 I I7.0 7.5 8.0 8.5 9.0 95
25BITUMEN CONTENT, %
20
FLORIDA LIMEROCK15 AC 20
GYRATORY COMPACTOR10 100 PSI,10 , 30 REVOLUTIONS
0-J 5
0 I I
7.0 7.5 8.0 8.5 9.0 9.5
BITUMEN CONTENT, %
Figure 4. Florida limerock mix design. Voidscalculated using bulk-impregnated specific
gravity
12
133 - 12 -
x132 - 10
S131-0X I,0
O 130 o 6
~O,.129 4
W UCL 128 cr 2
127 I I I0I I I-; 2000 90
1900 8 5
m1800 - L80
1700 0 75
25 --
,, 1600 w 70RC
1500 .5
1400 6
257.0 7.5 8.0 8.5 9.0 9.525 BITUMEN CONTENT, %
U) 20 FLORIDA LIMEROCK15. AC 20
S15GYRATORY COMPACTOR0 100 PSI, 10, 30 REVOLUTIONS
1NOTE: PLOTS FOR UNITWEIGHT,
5 STABILITY, AND FLOW ARE THES-J 5u. SAME AS THOSE SHOWN INFIGURE 4.
7.0 7.5 8.0 8.5 9.0 9.5
BITUMEN CONTENT, %
Figure 5. Florida limerock mix design. Voids calculatedusing theoretical maximum specific gravity--ASTM D 2041
total mix computed from the bulk-impregnated specific gravity and the
ASTM D 2041 specific gravity methods are shown in Figure 6. The specific
gravities used for the void calculations of the various asphalt contents are
listed in Table 4. The test results from ASTM D 2041 were an average of two
tests conducted on the material taken from the split sample, whereas the bulk-
impregnated specific gravities were calculated from an average of four tests.
13
FLORIDA LIME ROCK
100
90
SPECIFICATION LIMITSUj 50-BLOW DESIGN
+ 2.5% ABSORPTIONS80
0 o
70 do- MAXIMUM THEORETICAL.OPP SPECIFIC GRAVITY
Z 000004,ASTM D 2041
je 00-01 BULK-IMPREGNATED'Pap SPECIFiC GRAVITY
60
9
*~ MAXIMUM THEORETICALSPECIFIC GRAVITYASTM D 2041
7 SPECIFIC GRAVITY
0> h
A SPECIFICATION LIMITS3 50-BLOW DESIGN
+ 2.5% ABSORPTION
7.0 7.5 8.0 8.5 91) 9.5BITUMEN CONTENT,%
Figure 6. Florida limerock mix design.Comparison of voids filled and voids
total mix
14
Table 4
Comparison of Maximum Theoretical Specific Gravity
Florida LimerockASTM D 2041 Method
Percent Asphalt (Supplemental Procedure) Bulk-Impregnated Method
7.0 2.253 2.216
7.5 2.244 2.202
8.0 2.236 2.189
8.5 2.209 2.172
9.0 2.191 2.153
9.5 2.188 2.149
Alabama Limestone
14. A mix design was prepared for the Alabama limLstone aggregate and
AC 20 asphalt cement. The same tests conducted on the slag aggregate and the
Florida limerock were also conducted on the Alabama limestone aggregate.
15. Results of mix design tests conducted on the compacted samples are
shown in Figures 7 and 8. A comparison of the voids filled and the voids
total mix computed from the apparent specific gravity and the ASTM D 2041 max-
imum theoretical specific gravity is shown in Figure 9. The ASTM D 2041 test
method resulted in slightly higher voids total mix than did that calculated
from the apparent specific gravity. However, this difference is attributed to
testing variability and is within the acceptable range of single-operator
testing precision. The maximum theoretical specific gravities used for the
void calculations at the various asphalt contents are listed in Table 5. The
test results determined by the ASTh D 2041 method and the apparent specific
gravity method were an average of two tests conducted on the material taken
from the split sample.
Crushed Gravel
16. A mix design was prepared for the crushed gravel aggregate and
AC 20 asphalt cement. The same tests conducted on the slag aggregate, the
15
151 X 6
x 150
I 149 I- 4X 0
LUn
4 u 0 148 0t >aS147 -- w 2
9. U
2000 100 -
LU
1600 V2L380
-j>
v) 20 --
Fo 1400 70z
1200 160
Ow
1000 L so
25 5.0 5.5 6.0 6.5
BITUMEN CONTENT, %20 -2
wALABAMA LIMESTONE
_ 15 -AC 20
0 GYRATORY COMPACTOR
; Figure 7. Alabama limestone mix design.~Voids calculated using apparent specific
gravity
16
I~ ~ ~ ~ ~ ~ ~ ~ ~~~~~0 PS°I0 .. .. REVOLUT, ,, , 7 ... °" INS ' ..."""
151 X 6
150 5
-A~J 0I 149 - 4
=0
L 148 - 3
~r 147 - 2. Uw
146 _ . 1 C[
2000 -100
01800 . 90
.4 U.
1600 - 80!>
1400 i70
4L1200 - a 60 -
1000 _j 50
25 5.0 5.5 6.0 6.5
BITUMEN CONTENT, %0 20= 20ALABAMA LIMESTONE
15 AC 20S GYRATORY COMPACTOR
100 PSI,1, 30 REVOLUTIONS
ONOTE: PLOTS FOR UNIT WEIGHT, STABILITY.5 AND FLOW ARE THE SAME AS THOSE
SHOWN IN FIGURE 7.
05.0 5.5 6.0 6.5
BITUMEN CONTENT, %
Figure 8. Alabama limestone mix design. Voidscalculated using theoretical maximum specific
gravity--ASTM D 2041
17
ALABAMA LIMESTONE
100
SPECIFICATION LIMITS90 50-BLOW DESIGN
< 2.5% ABSORPTION 00
.0-
o-j
U.ca 70a0
60 --- @ MAXIMUM THEORETICALSPECIFIC GRAVITYASTM D 2041
U-U MAXIMUM THEORETICAL50 SPECIFIC GRAVITY
COMPUTED FROM APPARENTSPECIFIC GRAVITY
40 1I I I
6
0---O MAXIMUM THEORETICALSPECIFIC GRAVITY
5 ASTM D 2041UU MAXIMUM THEORETICAL
SPECIFIC GRAVITY
COMPUTED FROM APPARENTx 4 -SPECIFIC GRAVITY
o 3I- S PE CI F ICATIO"N LI ITS . . .
° sO~5-BLOW DESIGN =<2.5% ABSORPTION
0 I I I I4.5 5.0 5.5 6.0 6.5
BITUMEN CONTENT, %
Figure 9. Alabama limestone mix design.Comparison of voids filled and voids
total mix
18
' .... >... ': ~ ! ... ,, ,r, , , ,am . il ,
Table 5
Comparison of Maximum Theoretical Specific Gravity
Alabama LimestonePercent ASTM D 2041 Apparent Specific GravityAsphalt Method Method
5.0 2.529 2.510
5.5 2.505 2.491
6.0 2.484 2.473
6.5 2.469 2.455
Florida limerock, and the Alabama limestone were also conducted on the crushed
gravel.
17. Results of mix design tests conducted on the compacted samples are
shown in Figures 10 and 11. A comparison of the voids filled and the voids
total mix computed from the apparent specific gravity and the ASTM D 2041 max-
imum theoretical specific gravity is shown in Figure 12. The maximum theoret-
ical specific gravity calculated from the apparent specific gravity resulted
in percent voids total mix higher than did the ASTh D 2041 test method. The
maximum theoretical specific gravities used for the void calculations at the
various asphalt contents are listed in Table 6. The test results determined
by the ASTh D 2041 method and the apparent specific gravity method were an
average of two tests conducted on the material taken from the split sample.
Table 6
Comparison of Maximum Theoretical Specific Gravity
Crushed GravelPercent ASTM D 2041 Apparent Specific GravityAsphalt Method Method
7.0 2.358 2.381
7.5 2.340 2.365
8.0 2.323 2.348
8.5 2.303 2.332
19
142 7
141 ~-6 0
140 -50C
Uj 139 -> 4LL-
-D zC138 U. 3
137 _j2_
2000 100
4IL
1600 st: 08
~1400 i700 zI- U
"1200 (r60
1000 _j50 - I_
25 7.0 7.5 8.0 8.5BITUMEN CONTENT, %
~20
15 CRUSHED GRAVELAC 20
10 GYRATORY COMPACTOR100 P51,1 0, 30 REVOLUTIONS
IL 5
07.0 7.5 8.0 8.5
BITUMEN CONTENT, %
Figure 10. Crushed gravel mix design. Voidscalculated using apparent specific gravity
20
142 6
- 141 -j 5
4 0i- 140 I. 4
10
0 33 : 139 3
-u zLU 1:38 Lu 2
137 CL 1_
2000 100
0
C1800 - 70
US1600 - c 0
cn LUC-)
1000 _j 50
25 -7.0 7.5 8.0 8.5BITUMEN CONTENT, %
U 2020LU CRUSHED GRAVEL
S15 -AC 20GYRATORY COMPACTOR
10 100 PSI,1 0, 30 REVOLUTIONS
0 NOTE. PLOTS FOR UNIT WEIGHT, STABILITY.
IU. AND FLOW ARE THE SAME AS THOSESHOWN IN FIGURE 10.
07.0 7.5 8.0 85
BITUMEN CONTENT, %
Figure 11. Crushed gravel mix design. Voidscalculated using theoretical maximum specific
gravity--ASTM D 2041
21
CRUSHED GRAVEL
100
SPECIFICATION LIMITS90 50-BLOW DESIGN
< 2.5% ABSORPTION
80
,'7 0w
-J
-.70
0
a- 0 0- 6 MAXIMUM THEORETICALSPECIFIC GRAVITYASTM D 2041
U-U MAXIMUM THEORETICAL
50 SPECIFIC GRAVITYCOMPUTED FROM APPARENTSPECIFIC GRAVITY
40 I 1 1
7 *--- MAXIMUM THEORETICALSPECIFIC GRAVITY~ASTM D 2041
U-U MAXIMUM THEORETICAL6 SPECIFIC GRAVITY
COMPUTED FROM APPARENT6 ~SPECIFIC GRAVITYE
5~ ~ --- - - -
-J 4
SSPECIFICATION LIMITS
>50-B LOW DESIGNS < 2.5%ABSORPTION
0 I I I I
6s7.0 7.5 8.0 8.5BITUMEN CONTENT. %
Figure 12. Crushed gravel mix design. Comparison ofvoids filled and voids total mix
22
PART III: DISCUSSION
18. Figure 3 indicates that comparable void results can be obtained
when either the ASTM D 2041 or bulk-impregnated specific gravity test method
is performed on the slag aggregate to determine the maximum theoretical spe-
cific gravity. Figure 6, however, demonstrates a larger spread in the void
calculations when the two test methods were performed on the Florida limerock
aggregate. Figures 9 (Alabama limestone) and 12 (crushed gravel) compare the
voids determined from using the maximum theoretical specific gravity
(ASTM D 2041 method) with those determined using maximum theoretical specific
gravity computed from the apparent specific gravity. Comparable void results
are obtained when either test method is performed on the two nonabsorptive
aggregates (Alabama limestone and crushed gravel).
19. A possible explanation for the spread in the void results of the
Florida limerock aggregate is attributed to the physical makeup of the aggre-
gate. The slag aggregate has larger pores or voids than the limerock aggre-
gate. These voids tend to be filled with asphalt when slag is immersed and
stirred, as prescribed by the bulk-impregnated specific gravity test method.
When the ASTM D 2041 test procedure is used, these voids are filled with water
when the sample is subjected to a vacuum. The ability to fill these larger
openings when testing in accordance with the ASTM D 2041 method eliminates
most of the entrapment of air, which produces higher specific gravity results
than that computed for the bulk-impregnated specific gravity method. The
Florida limerock pores are much smaller than those in the slag aggregate and
are difficult to fill uniformly. In addition to the small pores, the limerock
is not uniform in structure; hence, varying degrees of porosity may be found
in the individual aggregate particles. These characteristics contribute to
the entrapment of air in the sample, resulting in lower bulk-impregnated spe-
cific gravity test results.
20. Table 7 presents a comparison of the percent voids in the total mix
using the ASTM D 2041 method with the voids calculated using the method speci-
fied in "Bituminous Pavements Standard Practice Manual" (TM 5-822-8)
(absorptive aggregate - bulk-impregnated specific gravity; nonabsorptive
aggregate - apparent specific gravity). The percent voids in the total mix
was determined at optimum asphalt content for each aggregate in the testing
23
program. The table indicates that the average value of percent voids in the
total mix of the absorptive aggregates is 3.6 percent using the bulk-
impregnated specific gravity test method, whereas the average value of percent
voids total mix is 4.4 percent using the ASTM D 2041 test method for determin-
ing maximum theoretical specific gravity. This indicates that the calculated
percent voids in the total mix for absorptive aggregate is increased by
approximately 1 percent when using the ASTM D 2041 test method. The void cri-
teria for absorptive aggregate should therefore be changed from 2- to
4-percent voids total mix to 3- to 5-percent voids total mix, and from 75- to
85-percent voids filled to 70- to 80-percent voids filled when using
ASTM D 2041 to obtain maximum theoretical specific gravity.
21. Table 7 also indicates that the average value of percent voids
total mix of the nonabsorptive aggregate is 3.3 percent using the ASTM D 2041
test method, whereas the average of percent voids total mix is 3.5 percent
using the apparent method for determining maximum theoretical specific grav-
ity. This indicated that comparable void results are obtained between the
ASTM D 2041 test method and the apparent method to obtain maximum theoretical
specific gravity for nonabsorptive aggregate.
Table 7
Comparison of Percent Voids Total Mix at
Optimum Asphalt Content
TM 5-822-8ASTM D 2041 Bulk-Impregnated Apparent
Aggregate Method Method Method
AbsorptiveSlag 3.9 4.0Florida limerock 4.8 3.2Average 4.4 3.6 -
NonabsorptiveCrushed gravel 3.0 - 4.0Alabama limestone 3.6 3.0Average 3.3 3.5
22. The ASTM D 2041 test method for determining maximum theoretical
specific gravity has been investigated on a number of recycled asphalt con-
crete paving jobs and found to produce satisfactory test results. This
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simplified testing procedure accelerates testing and reduces the margin of
error for recycled mixtures.
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PART IV: CONCLUSIONS
23. The following conclusions are based on observations and results of
tests conducted during the program:
a. The ASTM D 2041 test procedure is an acceptable replacement forthe bulk-impregnated test to determine the maximum theoreticalspecific gravity of asphalt mixtures containing absorptiveaggregates. Void criteria in the "Bituminous Pavements Stan-dard Practice Manual" (TM 5-822-8) should be changed from 2- to4-percent voids total mix to 3- to 5-percent voids total mix,and from 75- to 85-percent voids filled to 70- to 80-percentvoids filled when using ASTM D 2041 to determine the maximumtheoretical specific gravity of absorptive aggregate.
b. The ASTM D 2041 test procedure can be used as an alternate tocomputing the maximum theoretical specific gravity from theapparent specific gravities for nonabsorptive materials. Thevoid criteria should remain 3- to 5-percent voids total mix and70- to 80-percent voids filled when using ASTM D 2041 fornonabsorptive aggregate.
c. The ASTM D 2041 test procedure should be used on recycledasphalt material containing both absorptive and nonabsorptiveaggregates.
d. The ASTM D 2041 test procedure is a more realistic test thanthe bulk-impregnated specific gravity method to control asphaltmixes during field production in that it is performed on theactual material being manufactured and placed, whereas thebulk-impregnated specific gravity method is calculated duringmix design preparations and makes no allowances for variationsin materials during production.
e. Use of ASTM D 2041 for high absorption aggregates ensures thatmore testing laboratories are familiar with the test proce-dures, which should result in better control of the quality ofasphalt mixtures.
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REFERENCES
Buck, A. D. 1954 (May). "Investigation of the Penetration of Asphalt IntoPorous Aggregates as Related to and Affecting the Specific Gravity of theAggregate," Miscellaneous Paper No. 4-88, US Army Engineer Waterways Experi-ment Station, Vicksburg, Miss.
Department of Defense. 1966 (Jan). "Test Methods for Bituminous Paving Mate-rials," Military Standard 620A, Washington, DC.
Headquarters, Department of the Army. 1971 (Dec). "Bituminous PavementStandard Practice," Technical Manual (TM 5-822-8), Washington, DC.
McRae, J. L. 1955 (Feb). "Tests on Absorptive Aggregate to Study Effect ofAbsorption and Gradation on Voids in Compacted Bituminous Paving Mix," Miscel-laneous Paper No. 4-118, US Army Engineer Waterways Experiment Station,Vicksburg, Miss.
. 1956a (Feb). "Cooperative Study of Bulk Impregnated SpecificGravity," Miscellaneous Paper No. 4-152, US Army Engineer Waterways ExperimentStation, Vicksburg, Miss.
• 1956b (Mar). "Specific Gravity and Voids Relationships inBituminous Pavement Mix Design," Miscellaneous Paper No. 4-162, US Army Engi-neer Waterways Experiment Station, Vicksburg, Miss.
US Army Engineer Waterways Experiment Station. 1953. "Tentative Changes inVoids Criteria for Bituminous Paving Mixes When Using 'Bulk-Impregnated'Specific Gravity," Miscellaneous Paper No. 4-46, Vicksburg, Miss.
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